Study of genetic diseases with neoplastic manifestations and detailed investigation of families with high risk of cancer may help detect environmental and genetic influences in carcinogenesis, especially when appropriate laboratory assays are used. Besides results from our Clinical Studies Section and the Family Studies Unit of the Environmental Epidemiology Branch, laboratory reports were made on abnormal lymphocyte responses in four families with malignant melanoma complicating BK mole syndrome, an excess frequency of HLABw35 in 13 Hodgkin disease families, and in vitro radiosensitivities in a family with acute myelogenous leukemia and a radiogenic rectal carcinoma. A monograph on neurofibromatosis was edited and a collaborative NIH clinical-laboratory investigation of neurofibromatosis begun. Various groups of patients who survived cancer were studied for reproductive performance. Syndromes that do or may predispose to cancer were discovered or further delineated. Various methods to stimulate similar research were used including guest lectures, literature reviews, and participation in committee activities.